Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, the submersible pumping system includes a number of components, including one or more fluid filled electric motors coupled to one or more high performance pumps. Each of the components and sub-components in a submersible pumping system is engineered to withstand the inhospitable downhole environment, which includes wide ranges of temperature, pressure and corrosive well fluids.
Components commonly referred to as “seal sections” protect the electric motors and are typically positioned between the motor and the pump. In this position, the seal section provides several functions, including transmitting torque between the motor and pump, restricting the flow of wellbore fluids into the motor, protecting the motor from axial thrust imparted by the pump, and accommodating the expansion and contraction of motor lubricant as the motor moves through thermal cycles during operation. Many seal sections employ seal bags to accommodate the volumetric changes and movement of fluid in the seal section. Seal bags can also be configured to provide a positive barrier between clean lubricant and contaminated wellbore fluid.
In the past, seal bags have been constructed by sliding an open-ended bag over cylindrical mounting blocks. Hose clamps are used to secure the ends of the bag to the mounting blocks. Although generally acceptable, prior art bag mounting mechanisms suffer from several deficiencies. First, as the pressure inside the elastomer bag increases, the ends of the bag may axially slide over the mounting blocks, thereby allowing the bag to over-inflate. If the bag significantly over-inflates, the bag may rupture and the integrity of the seal section may be compromised.
Second, as the bag inflates during normal operation, the bag radially expands within a cavity in the seal section. The expansion of the bag may prevent proper fluid communication through the cavity around the exterior of the elastomer bag. There is therefore a need for an improved seal bag, seal sections and submersible pumping systems that overcome the deficiencies of the prior art. It is to this and other needs that the present invention is directed.